| With the great development of railway car and the improvement of people's living standard, the designers of trains pay much attention to increasing running speed and riding comfortableness in train design. The thermal comfortableness in carriage has become one of the most important targets in carriage design. Nowadays more and more trains are equipped with air conditioning system. The reason is they can be adjusted the air condition in carriage according to the change of climate. The traditional design of the air conditioning carriage takes only into account the total mass of airflow and total quantity of heat transfer, thus the distributions of air and temperature in the carriage can t be controlled accurately. In this paper, the situations of airflow and heat transfer for three carriage types were studied by numerical analysis method based on equations of fluid flow and heat transfer.The study work is a part of the project from one carriage manufactory which wants to analyze the flow field in the carriages. In this paper the numerical analysis method was used to realize the three-dimensional simulations for analyzing the temperature field and velocity field of carriages under the different air organization ways. The numerical simulation based on Navier-Stokes equation and k-ε turbulent model. The finite volume method was used to discretize the computed area. In the calculation a wall function was used to dealing with the boundary condition of calculating model. In addition, the upwind differencing scheme was used in the computation. And the SIMPLE algorithm was adopted to couple the velocity and pressure in flow field of the carriages. In the calculation, many kinds of heat transfer boundary conditions was taken into account, such as the heat transfer of walls, the heat transfer of solar radiate and the heat transfer radiating from human body.The buoyancy force aroused by difference of temperature was also considered. Finally, all calculation result were operated to get the following indexes: the coefficient of uniformity which could be used to evaluate the flow field;the ΔET and ADPI which could be used to evaluate the thermal comfort;the energy utilization factorwhich could be used to evaluate the economical efficiency.To summarize the rule of distribution characteristics of temperature field and velocity field and find out the key influential factors, this paper analyzed the computational results under three carriage types in detail. Then the paper gave out some modified working conditions and these conditions were proven to be effective. After the research, we could draw some useful conclusions: both the slotted inlet and grid inlet on ceiling are good air-supply form for hard-seat carriage, and the comfortable condition and good economical efficiency could be satisfied by choosing the appropriate temperature and velocity of inlet air. But in hard-sleeping carriage, the grid inlet on ceiling is not so good because of different structure of carriage and inappropriate location of inlet. So we tried to relocate the inlet on the carrier, and then found that the air organization and all the evaluating indexes have been improved. The traditional inlet on ceiling of soft-sleeping carriage can work well to get the good thermal comfort, but the new inlet located on the top of side walls can improve the homogeneous degree of flow field besides the thermal comfort.This research proves that it is feasible to analyze the air flow organization in the carriages of passenger trains using the numerical analysis method. The reasonable suggestions can be given to improve the thermal comfort and economical efficiency. The final conclusions offer some valuable guide lines to the future design of carriage. |
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